The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
In wireless communication systems, multiple-input and multiple-output (MIMO) refers to an use of multiple antennas at both a transmitter and a receiver to improve communication performance. MIMO technology has attracted attention in wireless communications, because MIMO offers significant increase in data throughput and link range without additional bandwidth or increased transmit power. MIMO achieves this by, for example, spreading the same total transmit power over the antennas to achieve an array gain that improves the spectral efficiency (e.g., more bits per second per hertz of bandwidth) or to achieve a diversity gain that improves a link reliability (e.g., reduced fading). Because of these properties, MIMO is an important part of various modern wireless communication systems.